Paste formulation for dental use, a paste injector, and a system for detecting of paste filling

ABSTRACT

A paste formulation for dental use, a paste injector, and a system for detecting paste filling are disclosed. The paste formulation includes electric conductive material. The present invention also discloses the system for detecting paste filling comprising a paste injector ( 1 ) containing electric conductive paste (D) and an electric conductive member for electrically connecting the electric conductive paste (D) to an external electrode, a current detector ( 101 ) for detecting the current flowing through the electric conductive paste (D) reserved in the container portion ( 1 ), and a current display device ( 105 ) for indicating the current flowing through the electronic conductive paste (D).

FIELD OF INVENTION

[0001] The present invention relates to a paste formulation, a tool, anda system for root canal treatment, more particularly relates to thepaste used for root canal filling, a paste injector, and a system usedtherewith.

BACKGROUND ART

[0002] In dental clinical treatments, root canal treatments arepopularly operated. Among the root canal treatments, root canal fillingis the stage operated at the final stage of the root canal treatment,and then the root canal filling has large effects on prognosis of adamaged tooth. Since the length to an apical constriction varies fromindividual patients, a length of the root canal must be measured. Amethod for this measurement includes, conventionally to measure anactual length of the tooth by using a reamer, a file, or a scale asdetection probes for an x-ray photograph. Recently, a method formeasurement of the root canal length using an impedance is widely used,because there is a case that the x-ray exposure is not adequate for apregnant woman and the impedance measurement is speedy and providesexact results.

[0003] The root canal length measurement by the impedance conventionallyuses a root canal meter etc. A working length is then determined to bethe reamer length inserted in the root canal minus 1 mm which isindicated by a predetermined impedance previously measured depending ona conditions of the instruments for measurement when a top of the reamercontacts to the periodontal membrane. Alternatively, the working lengthis determined as the length that gives current or resistance beingdifferent by a certain value from the value which indicates contact tothe periodontal membrane.

[0004] A root canal filling material, or root canal filling agent suchas a filler paste formulation conventionally used for the root canalfilling includes a gutta percha point used together with varioussealers, silver points and a filler in a paste formulation which may beformulated with a sustainable disinfectant or an accelerator for healingwith osteoid scar.

[0005] Especially, a method for filling the paste formulation in theroot canal portion includes filling the paste formulation through thereverse-rotated reamer operated by hand, filling by using a fillingdevice with a helical shape such as Rentulo plugger, or filling thepaste through a paste injector. However, the methods using the reamerand Rentulo plugger have disadvantages, because these methods require anextra procedure for measuring the root canal length and the specialdevice.

[0006]FIG. 9 shows a conventional method for filling the pasteformulation into the root canal by the injector. In the conventionalroot canal filling method using the injector, the injector 1 shown inFIG. 9(a) filled with the paste formulation M is used. The injector 1comprises a container portion 2 and an insert portion 3 which may beinserted into the container portion 2. A tube for injection of thefiller is disposed to a front end of the container portion 2 to form aninjection portion 4. In FIG. 9(a), the tip of the paste injection tubeis inserted into the root canal portion which has previously been spreadwidely.

[0007] In the conventional root canal filling method, as shown in FIG.9(b), the paste formulation M is injected into the root canal whileinserting the filler injection tube into the root canal and pressing theinsert portion 3 in the direction of the allow A. When the filling iscompleted, the filler injection tube is drawn out from the root canaland then the root canal filling operation is completed.

[0008] When the root canal is filled by the injector, as describedabove, an advantage to complete the injection easily and quickly may beprovided without the procedure to measure the root canal lengthpreviously. However, this method has yet some disadvantages, that is,filling of the paste to the apical constriction is unknown and the pasteformulation may irritate root peripheral tissues when the pasteformulation is injected beyond the apical constriction. When the fillingis not enough, a dead space and/or residual pulps may be allowed toexist. Therefore, there are needs for the paste formulation, the pasteinjector, and the system for detecting the paste filling.

DISCLOSURE OF THE INVENTION

[0009] In the first aspect of the present invention, a paste formulationfor dental use comprising electronic conductive material may beprovided.

[0010] In the first aspect of the present invention, the pasteformulation is provided, wherein the electronic conductive material ispowder.

[0011] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the electronicconductive material is selected from the group consisting of metalpowder, metal oxide powder, coated inorganic powder by metal and/ordoped metal oxide, carbon powder, carbon whisker, and whisker integratedwith metal.

[0012] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the pasteformulation includes at least one compound selected from the groupconsisted of calcium hydroxide, hydroxy apertite, tricalcium phosphate.

[0013] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the pasteformulation includes at least one compound selected from the groupconsisting of iodoform, barium sulfate, anhydrous zinc sulfate, aluminumsulfate, and zinc oxide.

[0014] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the pasteformulation includes at least one vehicle selected from the groupconsisting of silicone oil, guaiacol formaldehyde mixture, propyleneglycol, dry ethanol, caster oil, liquid paraffin.

[0015] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the pasteformulation includes at least one compound selected from the groupconsisting of iodoform, barium sulfate, anhydrous zinc sulfate, aluminumsulfate, and at least one vehicle selected from the group consisting ofsilicone oil, guaiacol-formaldehyde mixture, propylene glycol, dryethanol, caster oil, and fluid paraffin.

[0016] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the pasteformulation includes an x-ray contrast agent.

[0017] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the electronicconductive material is present between 5-50 wt % based on a solid of thepaste formulation.

[0018] In the first aspect of the present invention, the pasteformulation for dental use may be provided, wherein the pasteformulation includes at least one compound selected from the groupconsisting of calcium hydroxide, hydroxy apertite, tricalcium phosphatenot less than 30 wt % based on a solid of the paste.

[0019] In the second aspect of the present invention, a paste injectormay be provided. The paste injector comprises;

[0020] a container portion within which electric conductive paste isreserved,

[0021] an insert portion inserted into the container portion,

[0022] an injection portion for injecting the electric conductive pasteformulation into a constricted portion portion, and

[0023] an electric conductive member for electrically connecting theelectrically conductive paste formulation to an external electrode.

[0024] In the second aspect of the present invention, the paste injectormay be provided, wherein the electric conductive member comprises aterminal exposed at an end face of the insert portion inserted into thepaste container portion and contacting to the electric conductive pasteformulation, a terminal disposed at the insert portion and exposedoutside the insert portion, and a lead line connecting between theterminals.

[0025] In the second aspect of the present invention, the paste injectormay be provided, wherein the electric conductive member is insertedthrough the insert portion.

[0026] In the second aspect of the present invention, the paste injectormay be provided, wherein the electric conductive member comprises an endextending through an inner path of the injection portion, an end drawnout of the paste injector, and a lead line connecting between the ends.

[0027] In the third aspect of the present invention, a system fordetecting paste filling may be provided. The system comprises;

[0028] a paste injector comprising an electric conductive pasteformulation and an electric conductive member for electricallyconnecting the electric conductive paste to an external electrode,

[0029] a current detector for detecting the current flowing through theelectric conductive paste formulation injected into a constrictedportion, and

[0030] a current display device for indicating the current flowingthrough the electronic conductive paste.

BRIEF EXPLANATION OF DRAWINGS

[0031]FIG. 1 shows the paste injector according to the presentinvention;

[0032]FIG. 2 shows details of the paste injector according to thepresent invention;

[0033]FIG. 3 shows a second embodiment of the paste injector accordingto the present invention;

[0034]FIG. 4 shows an arrangement of a conventional system for impedancemeasurement used for detecting the working length;

[0035]FIG. 5 shows a method for the root canal length measurement usingthe reamer and the impedance;

[0036]FIG. 6 shows an arrangement for filing electronic conductive pasteD into the root canal of the damaged tooth by the paste injector of afirst embodiment according to the present invention;

[0037]FIG. 7 shows an arrangement for filing electronic conductive pasteD into the root canal of the damaged tooth by the paste injector of asecond embodiment according to the present invention in the samearrangement shown in FIG. 6;

[0038]FIG. 8 shows an electric circuit arrangement used for testing thepaste according to the present invention; and

[0039]FIG. 9 shows a conventional root canal filling method by aconventional injector.

BEST MODE FOR CARRING OUT THE INVENTION

[0040] The present invention provides an electric conductive pasteformulation for the dental treatment, i.e., an electric conductive pasteformulation, a paste injector, and a system for detecting paste filling.Hereafter, the electric conductive paste formulation, the pasteinjector, and the system for detecting paste filling will be describedusing the drawings attached when necessary.

[0041] The electric conductive paste formulation according to thepresent invention may be formulated by mixing a suitable electricconductive material to conventional compositions for forming of calciumhydroxide paste, zinc eugenol pasta, iodoform paste, paraform-formalinepaste. These conventional paste compositions may include Triozinc pastawhich is a mixture of paraform aldehyde, anhydrous zinc sulfate,aluminum sulfate, potassium sulfate, zinc oxide mixed with cresol,phenol, and creosote; Kri 1 which is a mixture of iodoform powder,parachrolophenol camher, menthol, lanolin, glycerin; Carbitar which is amixture of iodoform powder, calcium hydroxide powder, sulfathiazolepowder, guanofuracin with a vehicle such as Tcaine and guanofuracin;Bitapex which is a mixture of calcium hydroxide powder and iodoformpowder with silicone oil; FR which is a mixture of calcium hydroxidepowder, zinc oxide powder, barium sulfate powder, and a vehicle such asguaiacolformaldehyde mixture, propylene glycol, dry ethanol, caster oil,liquid paraffin; Sealapex which comprises a polymer resin and calciumhydroxide.

[0042] Other paste formulation such as Endofil which uses a polymericmaterial as a base and the paste formulations which use hydroxy apatiteor tricalcium phosphate may be useful, because such paste formulationsexhibit affinity to live tissues and accelerate hard tissues formation.These paste formulations may provide advantages that the formulation maybe absorbed by the tissues if the paste formulation runs out from theapical constriction. The above described calcium hydroxide, hydroxyapatite, tricalcium phosphate may be included in the electric conductivepaste in an amount not less than 30 wt %, more preferably not less than50 wt % based on the weight of solid contents in the electric conductivepaste formulation.

[0043] The electric conductive material suitably used in the presentinvention may include electric conductive powder so as to be mixedsufficiently with the above described paste formulations. Suchelectronic conductive powder may have a particle size between 200 Å˜100μm, more preferably, between 0.01·80 μm, most preferably between 10˜50μm in order to achieve a good filing performance. Shapes of the electricconductive powder may be a spherical shape, a needle shape, and a scaleshape.

[0044] The powder may include metal powder such as, for example, goldpowder, silver powder, copper powder, nickel powder, metal oxide powdersuch as, for example, ZnO, SnO₂, I₂O₃, ITO, various doped metal oxidessuch as antimony doped SnO₂, BaSO₄ coated with metal, SnO₂, or otherelectric conductive materials, TiO₂ powder coated by Ag, TiO₂ powdercoated with Sn₂, electric conductive carbon black, powder having highaspect ratio such as, for example, potassium titanate whisker coatedthereon by Ag or Pd, whisker coated thereon by SnO₂, electric conductivecarbon whisker. Particularly, needle type powder may provide an improvedvolume resistivity of the electric conductive paste formulation with lowcontents.

[0045] The above described electric conductive paste may have volumeresistivity from 10⁻² Ωcm to 10⁶ Ωcm, and it is preferred that theresistance of the electric conductive paste formulation when injected inthe root canal portion may exhibit resistance in an order of theresistance through the periodontal membrane. As described below, if thevolume resistivity is too high, the detection of the paste injection maynot provide sufficiently exact results.

[0046] The electric conductive powder may be present in the electricconductive paste formulation so as to provide the required volumeresistivity to the electric conductive paste formulation, and the powdermay present from 5 wt %˜50 wt % based on the solid of the pasteformulation, more preferably present from 10 wt %˜30 wt % based on thesolid of the paste formulation.

[0047] The vehicles may present in the electric conductive pasteformulation from 10 wt %˜70 wt %, more preferably from 30 wt %˜60 wt %.

[0048] Hereinbelow, an exemplary embodiment of the paste formulationincluding calcium hydroxide as its major component and electricconductive metal powder will be explained.

[0049] First, calcium hydroxide is prepared. This calcium hydroxide maybe used under the specification of Japanese Pharmacopoeia having theparticle size from 10˜50 μm.

[0050] In this electric conductive paste, iodoform may preferably bepresent, because an anti-bacterial activity may be extremely enhanced,and an x-ray imaging performance may be also improved.

[0051] In addition, the vehicle described above such as silicone oiletc. may be added to calcium hydroxide. Addition of the silicone oil mayprovide an anti-corrosion property to the paste formulation as well asproviding an adequate flow performance.

[0052] Other additives to the calcium hydroxide may be selected fromvarious types. For example, when x-ray contrast agents including bismuthbicarbonate, bismuth sulfate, zirconium silicate may improve the x-rayimaging performance of the paste.

[0053] A dispersion method for the powder may be selected from anywell-known conventional dispersion methods. Especially, when theelectric conductive powder having the particle size between 10 and 50 μmis used as described above, it is possible to apply various mixingand/or dispersion methods, because aggregation of the powder may not beso severe. In the preparation of the electric conductive pasteformulation according to the present invention, the paste formulationmay be prepared, for example, by providing a paste formulation which ispremixed with calcium hydroxide, iodoform, and silicone oil, adding theelectric conductive powder, mixing the resulted paste formulation againto formulate the electric conductive paste formulation, then filling theresulted electric conductive paste formulation into the injector in aform of a cylinder for use when necessary. However, it is possible tomix a non-conductive powder such as calcium hydroxide and the electricconductive powder together with the vehicle such as silicone oil at thesame time so far as the paste formulation according to the presentinvention may be obtained.

[0054] In the above described embodiment, the conductivity/ resistivitydescribed above may be obtained by adding electric conductive powdersuch as gold, silver, copper, and nickel having the particle sizedescribed above. Since the electronic conductivity is provided with thepaste formulation, and the paste formulation may be injected into theroot canal by an injector implemented with an electric conductivemember, the adequate injection of the paste formulation to the rootcanal may be proofed by detecting the resistance. Further, since theelectric conductive powder is added in the paste, and the thermal andelectronic conductivities of the paste are improved so that good thermaland electric feelings may be obtained. When the carbon powder is used,it is expected to absorb formaldehyde included in form-cresol which isused to treat the root canal and is also included as the major componentof form-cresol.

[0055] Referring to figures, an embodiment of the paste injector, whichis able to inject the electric conductive paste formulation into theroot canal and simultaneously to measure the electric resistance, willbe explained in detail.

[0056]FIG. 1 shows an exploited view of a first embodiment of the pasteinjector 1 according to the present invention. The paste injector 1comprises the container portion 2 for reserving the electric conductingpaste formulation, the insert portion 3 being inserted into thecontainer portion 2, the injection portion 4 formed as a tapered tubetoward the tip and disposed at the front end of the container portion 2,and the seal member 5 disposed at the end of the insert portion 3 whichis inserted to the container portion 2.

[0057] The container portion 2 and the insert portion 3 may be made ofglass, or synthetic resin such as polypropyrene, polycarbonate,polyvinyl chloride. However, when a handling performance such as damageis considered, the portions 2, 3 may preferably be made of a syntheticresin such as polypropyrene, polycarbonate, polyvinyl chloride. Thecontainer portion 2 has a hollow inside portion within which theelectric conductive paste formulation is reserved. The container portion2 comprises a projection 2 a at the end opposite to the injectionportion 4 with which insertion of the insert portion 3 is made easy whenfingers are rest thereon. Materials for forming the injection portion 4may be selected from any materials as far as the shape of the taperedtube of the injection portion 4 is formed to be thin and flexible.

[0058] The insert portion 3 is used to extrude the electric conductivepaste formulation reserved in the container portion 2. The seal member 5disposed at the front end of the insert portion 3 improves the sealbetween the inner face of the container portion 2 and insert portion 3.Installation of the seal member 5 to the insert portion 3 may beachieved through various methods including engaging the seal member 5 inthe shape of pipe onto a recess formed to the insert portion 3, ormolding the seal member 5 made of a synthetic resin integrally aroundthe insert portion 3.

[0059] At the end of the insert portion 3 opposite to the end insertedinto the container portion 2 comprises the projection 3 a extendingbeyond the diameter of the insert portion 3 so as to make the inset easyby exerting force by fingers when the electric conductive pasteformulation is injected into the root canal. The projection 3 a may beformed separately from the container portion 3 and then may be adheredby some types of adhesives as well as being integrally formed with thecontainer portion 3.

[0060] When the electronic conductive paste formulation is injected intothe root canal, the above described paste injector 1 is held by onehand, and clipping the projections 2 a, 3 a between the fingers to exertthe force to extrude the electric conductive paste formulation into theroot canal.

[0061] As shown in FIG. 1, the first embodiment of the insert portion 3of the paste injector 1 according to the present invention isimplemented with the conductive member. The conductive member comprisesthe end 6, the terminal 7, the end 8, the terminal 9, and the lead line10 extending between the end 6 and the end 7. These components forms theconductive member by the end 6 being connected to the terminal 7 formedon the side of the seal member 5 which contacts to the electricconductive paste formulation. Another end 8 is connected to the terminal9 extending outside the insert portion 3 from the position adjacent tothe projection 3 a formed on the insert portion 3. The lead line 10extends through the insert portion 3, thereby the electric conductivepaste formulation being connected electrically outside the insertportion 3. The lead line 10, the terminals 7, 9 may be implemented byinsert molding when the insert portion 3 is molded, or by inserting themafter molding thereof.

[0062]FIG. 2 shows an enlarged cross section of the terminal connectingportion of the terminal 9 of the first embodiment of the paste injector1 according to the present invention. FIG. 2(a) shows an enlarged crosssection of the insert portion 3 comprising the terminal 9. As shown inFIG. 9(a), the terminal 9 extends outside the insert portion 3 from theposition adjacent to the projection 3 a and the electrode 106 isconnected to the terminal 9 through the clip. FIG. 2(b) shows that theterminal 9 is disposed in the projection 3 a, and protrudes outside theinsert portion 3 from the lateral side of the projection 3 a. FIG. 2(c)shows that the terminal 9 has the opening 11 facing outside the insertportion 3 into which a needle electrode may be inserted or screwed. FIG.2(d) shows that the terminal 9 is formed as the band which extendscircumferencially and radially about the insert portion 3 at theposition adjacent to the projection 3 a of the insert portion 3. Thearrangement of the terminal 9 illustrated in FIG. 2 may be selecteddepending on easiness of handling and operation for the root canalfilling, and the constructions shown in FIG. 2 may be used in anycombinations each other.

[0063]FIG. 3 shows a second embodiment of the paste injector 1 accordingto the present invention. FIG. 3(a) shows a partial cut away crosssection of the paste injector 1, and the paste injector 1 comprises thecontainer portion 2, the insert portion 3 which is inserted into thecontainer portion 2. The injection portion 4 is formed to the taperedtube and is disposed at the front end of the container portion 2. InFIG. 3(a), the container portion 2 is partly cut away to show theelectronic conductive paste formulation D. In the injection portion 4 ofthe paste injector 1 of the second embodiment according to the presentinvention, the lead line 10 extends outside the paste injector 1 atabout the curved portion thereof so that distance between a tip of theinjection portion 4 and the end of the lead line 10 may be substantiallydecreased with respect to the first embodiment so as to reduce adverseeffects of the resistance of the electric conductive paste formulation Don the resistance measurement.

[0064] In FIG. 3(b), an enlarged cross section of the curved portion ofthe injection portion 4 attached to the paste injector 1 is shown. Thesecond embodiment of the paste injector 1 shown in FIG. 3(b) has thelead line 10 extending through the inside path 4 a adjacent to the tipfrom the lead line inlet position formed at the injection portion 4 asclose as possible such that the end 6 may be located adjacent to the tipfrom which the electric conductive paste D is injected. When suchconstruction is adopted, the distance between the end 6 and anotherelectrode 104 (not shown) through the electric conductive pasteformulation D may be reduced, thereby reducing the effect on theresistance measurements due to the resistance of the electric conductivepaste formulation D.

[0065] When the lead line 10 is drawn out of the paste injector 1 of thesecond embodiment according to the present invention, the terminals 9shown in FIG. 2 may be used. Alternatively, without providing theterminal 9, the lead line 10 is stripped at the both ends to obtainsufficient conductivity such that one end is disposed in the inner path4 a. Another end may be drawn outside the wall of he injection portion 4c while maintaining seal performance with a heat-seal or the adhesive 4b. It is of course possible to mold the lead line 10 integrally when theinjection portion 4 is molded. The lead line 10 drawn out of the pasteinjector 1 may be extended to the projection 2 a formed to the containerportion 2 along to the outer lateral side so as not to contact thestripped end to an oral cavity, and thereafter be connected to anelectrode of the apparatus for measuring resistance. The lead line usedmay have any thickness. However, to obtain good handling performancewhile not degrading the injection through the injection portion 4, thelead line 10 may preferably be thin sufficiently. The lead line 10 mayhave a cover, or may not have a cover.

[0066] Now, a system for detecting the paste filling will be explainedhereinbelow with referring to FIG. 4˜Fi. 7. FIG. 4 shows a conventionalarrangement of a system for measuring the root canal length by theresistance or the impedance. When the root canal length is measured bythe resistance conventionally, the operation thereof comprises steps of;first spreading the root canal portion of the damaged tooth T, nextcleaning the spread root canal 21 by hydrogen peroxide while remaininghydrogen peroxide within the root canal 21, and then inserting thereamer 20 into the root canal 21.

[0067] The resistance measuring device 100 comprises the currentdetector 101, the power supply 102, the control device 103 includingrelay circuit, the electrode 104 connected to the damaged tooth throughlip, the current display device 105 including a current indicationdevice and/or an alarm device, and the electrode 106 connected to theend of the reamer 20. The resistance measuring device 100 actuates thecurrent display device 105 through the control device 103 based on thecurrent signal detected by the current detector 101. The resistancemeasuring device 100 acknowledges to the operator that the resistancesor the current values become a predetermined values, or the top of thereamer reaches to the apical constriction P, or the top of the reamerreaches to the position having a predetermined distance, i.e., about 1mm from the apical constriction P.

[0068] Usually, when the reamer 20 reaches to the periodontal membrane,the electric circuit formed between the reamer 20 and the electrode 104which is connected to a tube contacting to a lip and being extended froma dental pump has a resistance about 6.5 kΩ including an internalresistance of the system for resistance measurement. FIG. 5 shows aschematic illustration of the resistances. In FIG. 5, the resistance ofthe reamer 20 is shown by the reference numeral R1. As shown in FIG. 5,the reamer 20, the periodontal membrane, and the electrode 104 usuallyconnected to the dental tube form an electric circuit including aresistance R1. Usually, the inside of the root canal in which the reamer20 is inserted is cleaned and is almost dried under the measurement.Therefore, the current may not substantially flow in the circuit.However, the current becomes to flow due to effects of exudate, and/orconductivity of hydrogen peroxide used in the cleaning process andremained therein as the top of the reamer 20 moves toward theperiodontal membrane. When the reamer 20 reaches to the periodontalmembrane, the entire circuit resistance becomes to the above explainedresistance of about 6.5 kΩ.

[0069] The present invention uses the electric conductive pasteformulation D as a probe electrode rather than using the reamer 20 asthe probe electrode for the measurement of the root canal length.

[0070]FIG. 6 shows an arrangement when the electric conductive pasteformulation is filled in the root canal 21 of the damaged tooth T usingthe paste injector 1 according to the first embodiment of the presentinvention. As shown in FIG. 6, the terminal 9 is connected to theelectrode 106 of the resistance measurement device 100, and theelectrode 104 of the resistance measurement device 100 is connected tothe dental tube. In the condition illustrated in Fig, 6, no current, orvery low current flows through the current detecting device 101, andthen the resistance is held high.

[0071]FIG. 7 shows the filling process of the electric conductive pasteformulation D into root canal 21 using the same arrangement shown inFIG. 6 while the paste injector 1 according to the second embodiment ofthe present invention being used. As shown in FIG. 7, as the filling ofthe electric conductive paste formulation D proceeds and the electricconductive paste formulation D becomes closer to the apical constrictionP, a week current start to flow through the electric conductive pasteformulation D. Finally the electric conductive paste D contacts to theperiodontal membrane, and then the resistance R1 of the reamer 20 isreplaced to the resistance R2. The resistance R2 depends on the distancebetween the position where the lead line 10 contacts to the electricconductive paste formulation D within the injection portion 4 and theperiodontal membrane. Therefore, the detection of the filing of theelectric conductive paste formulation D to the apical constriction P isdetermined by monitoring the resistance to be (6.5 kΩ−R1+R2).Alternatively, the relation between the distance from the periodontalmembrane to the electric conductive paste formulation D includingconductive metals, or conductive metal oxides and the resistance ispreviously measured by x-ray photographs, and then the distance from theperiodontal membrane may be estimated when the resistance reaches to acertain resistance higher than (6.5 k Ω−R1+R2). As described above,since the present invention uses the paste formulation filled in theroot canal as the current probe, once the resistance reaches to theabove certain value, it is determined that the filling of the root canalby the paste formulation is completed. The construction described aboveallows to reduce complexity of the root canal filing and/or injectionoperation that previously requires duplex steps; measuring the rootcanal length by the impedance, and next spreading the root canal portionand then inserting the gutta percha point to complete the filling of theroot canal. In addition, the detection whether or not the pasteformulation is filled within the root canal sufficiently becomes easywhereas such detection is regarded to be difficult in the conventionalroot canal filling/injection operation. Therefore, the present inventioncan provide the system for detecting of paste filling which makes themeasurement more speedy and easier, and that ensures the filling of thepaste formulation.

[0072] The power supply 102 used may be selected from a direct currenttype or an alternative current type, and the value of R2 and theinternal resistance etc. may be selected as requested. The measurementetc. may be achieved through the resistance measurement or the impedancemeasurement depending on the kinds of the power supplies used. It maypossible to alarm the operator to pay attention when the predeterminedworking length is obtained.

[0073] Hereafter, the present invention will be explained in detail byexamples, however, these examples are provided only for explanation ofthe present invention and do not intend to limit the scope of thepresent invention.

EXAMPLES Example 1

[0074] To a solid component including 50 wt % of calcium hydroxyde,iodoform 20 wt %, 30 wt % of silicone oil was added and mixed to preparea paste formulation.

[0075] To this paste formulation, further 10 wt % of a silver powderbased on the weight of the above solid component was added and mixed toform the paste formulation according to the present invention. Thecurrent of 5 mA was flew in the resulted electric conductive pasteformulation as measured by an ampere meter. Next, a lead line having 0.1mm diameter was inserted to a injection portion of a commerciallyavailable paste injector so as to prepare the paste injector accordingto the present invention as shown in FIG. 3. The electric conductivepaste as prepared above was filled in the paste injector, and the pastedischarge through the tip portion was confirmed.

[0076] A circuit illustrated in FIG. 8 was constructed using a pulplesstooth and injecting the electronic conductive paste formulation into theroot canal 21 using the paste injector in order to operate the rootcanal filling. The front end of the electrode 104 of the resistancemeasurement device 100 was located inside the root canal 21 slightlyabove the apical constriction P. As the injection of the electricconductive paste formulation was started and was proceeded, the currentdetector 101 detect the current through the circuit shown in FIG. 8.

[0077] Thereafter, the injection portion of the paste injector waspulled out carefully from the pulpless tooth, and an x-ray photographwas taken to observe the filling condition of the electric conductivepaste formulation. It was confirmed that the electronic conductive pasteformulation reached to the apical constriction P. That is, the detectionof the circuit formation by the electronic conductive paste formulationbeing reached to the apical constriction P indicates the completion ofthe root canal filling.

Example 2

[0078] 40 wt % of hydroxy appertite, 10 wt % of barium sulfate, 50 wt %of silicone oil were mixed together to form the paste formulation. Aupowder of 25 wt % was mixed to the above paste formulation. The currentof 3 mA flew in the resulted paste as measured by the ampere meter. Theresulted electric conductive paste formulation was used in the same testas described in the Example 1. It was confirmed that the electricconductive paste was filled in the apical constriction P of the damagedtooth.

[0079] Indusrial Availability

[0080] As described above, since the present invention uses the pasteformulation filled in the root canal as the current probe, thecompletion of the paste formulation into the root canal is immediatelydetected when the resistance becomes the above described value.Therefore, conventional duplex procedures comprising measuring the rootcanal length by the impedance measurement, next spreading the rootcanal, and then inserting the gutta percha point so as to fill the rootcanal is not required. In addition, the detection whether or not thepaste is entirely filled in the root canal becomes easy, which wasdifficult in the conventional root canal filling operation using thepaste. The present invention may provide the system for detecting ofpaste filling which is carried out more speedy and easier while ensuringthe filling of the paste sufficiently.

[0081] The present invention has been explained by non-limitingexemplary examples, however, it is appreciated by a person skilled inthe art that many other variations, modifications, and omissions may bepossible within the scope of the invention as described in the appendedclaims. True scope of the present invention will only be limited by theclaims.

I claim;
 1. A paste formulation for dental use comprising electronicconductive material.
 2. The paste formulation for dental use accordingto the claim 1, wherein the electronic conductive material is powder. 3.The paste formulation for dental use according to the claim 1, whereinthe electronic conductive material is selected from the group consistingof metal powder, metal oxide powder, coated inorganic powder by metaland/or doped metal oxide, carbon powder, carbon whisker, and whiskerintegrated with metal.
 4. The paste formulation for dental use accordingto the claim 1, wherein the paste formulation includes at least onecompound selected from the group consisted of calcium hydroxide, hydroxyapertite, tricalcium phosphate.
 5. The paste formulation for dental useaccording to the claim 1, wherein the paste formulation includes atleast one compound selected from the group consisting of iodoform,barium sulfate, anhydrous zinc sulfate, aluminum sulfate, and zincoxide.
 6. The paste formulation for dental use according to the claim 1,wherein the paste formulation includes at least one vehicle selectedfrom the group consisting of silicone oil, guaiacol formaldehydemixture, propylene glycol, dry ethanol, caster oil, liquid paraffin. 7.The paste formulation for dental use according to the claim 5, whereinthe paste formulation includes at least one compound selected from thegroup consisting of iodoform, barium sulfate, anhydrous zinc sulfate,aluminum sulfate, and at least one vehicle selected from the groupconsisting of silicone oil, guaiacol-formaldehyde mixture, propyleneglycol, dry ethanol, caster oil, and fluid paraffin.
 8. The pasteformulation for dental use according to the claim 1, wherein the pasteformulation includes an x-ray contrast agent.
 9. The paste formulationfor dental use according to the claim 1, wherein the electronicconductive material is present between 5˜50 wt % based on a solid of thepaste formulation.
 10. The paste formulation for dental use according tothe claim 1, wherein the paste formulation includes at least onecompound selected from the group consisting of calcium hydroxide,hydroxy apertite, tricalcium phosphate not less than 30 wt % based on asolid of the paste.
 11. A paste injector comprising; a container portionwithin which electric conductive paste is reserved, an insert portioninserted into the container portion, an injection portion for injectingthe electric conductive paste formulation into a constricted portion,and an electric conductive member for electrically connecting theelectrically conductive paste formulation to an external electrode. 12.The paste injector according to the claim 11, wherein the electricconductive member comprises a terminal exposed at an end face of theinsert portion inserted into the paste container portion and contactingto the electric conductive paste formulation, a terminal disposed at theinsert portion and exposed outside the insert portion, and a lead lineconnecting between the terminals.
 13. The paste injector according tothe claim 12, wherein the electric conductive member is inserted throughthe insert portion.
 14. The paste injector according to the claim 11,wherein the electric conductive member comprises an end extendingthrough an inner path of the injection portion, an end drawn out of thepaste injector, and a lead line connecting between the ends.
 15. Asystem for detecting paste filling comprising; a paste injectorcomprising an electric conductive paste formulation and an electricconductive member for electrically connecting the electric conductivepaste to an external electrode, a current detector for detecting thecurrent flowing through the electric conductive paste formulationinjected into a constricted portion, and a current display device forindicating the current flowing through the electronic conductive paste.16. A paste injector for dental use comprising: a container portion forholding a mixed electric conductive paste, said electric conductivepaste comprising 5-50 weight % of electric conductive powder based on asolid component of said electric conductive paste, at least one compoundselected from the group consisted of calcium hydroxide, hydroxy apatiteand tricalcium phosphate, and at least one vehicle selected from thegroup consisted of silicone oil, guaiacol formaldehyde mixture,propylene glycol , dry ethanol, caster oil, liquid paraffin; an insertportion inserted into said container portion; an injection portion forinjecting into a constricted portion and having an inner path forguiding said electric conductive paste to said constricted portion, saidinjection portion being connected to said container portion so as toreceive said electric conductive paste pressured by said insert portion,and an electric conductive member for electrically connecting saidelectrically conductive paste to an external electrode positionedoutside said paste injector.
 17. The paste injector for dental useaccording to claim 16, wherein said constricted portion is a root canal.18. The paste injector for dental use according to claim 16, whereinsaid insert portion has a first end, and said electric conductive membercomprises a first terminal exposed at a face of said first end of saidinsert portion and contacting said electric conductive paste, a secondterminal disposed at said insert portion and exposed outside said insertportion so as to electrically connect said electrically conductive pasteto an external electrode positioned outside said paste injector, and alead line connecting between said first terminal and said secondterminal.
 19. The paste injector for dental use according to claim 18,wherein said lead line of said electric conductive member is insertedthrough said insert portion between said first end and said second end.20. The paste injector for dental use according to claim 16, whereinsaid electric conductive member comprises a first end extending throughsaid inner path of said injection portion, a second end drawn out ofsaid paste injector, and a lead line connecting between said first endand said second end.
 21. The paste injector for dental use according toclaim 16, wherein the paste is premixed.
 22. A system for detectingpaste filling comprising: a paste injector comprising a containerportion for holding a mixed electric conductive paste, said electricconductive paste comprising 5-50 weight % of electric conductive powderbased on a solid component of said electric conductive paste, at leastone compound selected from the group consisted of calcium hydroxide,hydroxy apatite and tricalcium phosphate, and at least one vehicleselected from the group consisting of silicone oil, guaiacolformaldehyde mixture, propylene glycol , dry ethanol, caster oil, liquidparaffin; an insert portion inserted into said container portion; aninjection portion for injecting into a constricted portion and havinginner path for guiding said electric conductive paste to saidconstricted portion, said injection portion being connected to saidcontainer portion so as to receive said electric conductive pastepressured by said insert portion; and an electric conductive member forelectrically connecting said electrically conductive paste to anexternal electrode positioned outside said paste injector; a currentdetector for detecting current flowing between said electric conductivepaste injected into said constricted portion and said externalelectrode; and a current display device for indicating said currentflowing through said electric conductive paste filled into saidconstricted portion.
 23. A system according to claim 22, wherein saidconstricted portion is a root canal.
 24. A system according to claim 22,wherein said paste is premixed.